Inlays for filling cavities in teeth are frequently made of metal, such as silver. These inlays have relatively long lifetimes, but they are not aesthetically pleasing, being visible in the mouth as a gray area. Patients with pure metal inlays are frequently self-conscious when smiling or yawning. Because natural dentin is translucent and allows a significant amount of visible light to pass through it, metal inlays in the center of even large teeth, such as molars, can be visible as a grayish, dead-looking spot in the patient's mouth.
One alternative to such solid metal inlays is the use of inlays made of plastic. While such plastic inlays are easy to work with and present acceptable aesthetic characteristics, such inlays have inferior wear characteristics. Plastic inlays wear extremely quickly, especially in occlusal inlays.
Another alternative is an inlay made of translucent ceramic material. These ceramic inlays are also aesthetically pleasing because ceramic is similar to the natural tooth structure. Thus, such inlays alleviate much of the patient's mental discomfort regarding mouth appearance. However, these ceramic inlays also have inferior strength characteristics. Because such inlays lack support, they tend to fracture after a few years of normal occlusions with opposing teeth. Moreover, inlays made of ceramic tend to fracture at the margin (the edge of the inlay adjacent the remainder of the natural tooth). In such cases, it is likely that organic matter will become lodged between the fractured inlay and the remainder of the natural tooth, leading to further tooth decay.